The present invention relates generally to the field of electric utility meters. More particularly, the present invention relates to both electronic watthour meters and meters utilized to meter real and reactive energy in both the forward and reverse directions.
Techniques and devices for metering the various forms of electrical energy are well known. Meters, such as utility power meters, can be of two types, namely, electromechanical based meters whose output is generated by a rotating disk and electronic based meters whose output component is generated electronically. A hybrid meter also exists, wherein an electronic register for providing an electronically generated display of metered electrical energy has been combined, usually optically, to a rotating disk. Pulses generated by the rotating disk, for example by light reflected from a spot painted on the disk, are utilized to generate an electronic output signal.
It will be appreciated that electronic meters have gained considerable acceptance due to their increasing reliability and extended ambient temperature ranges of operation. Consequently, various forms of electronic based meters have been proposed which are virtually free of any moving parts. In the last ten years several meters have been proposed which include a microprocessor.
Testing of electronic meters has always been a problem. A special mode of register operation known in the industry as the test mode has been available to ease register testing, however, little has been done to improve overall meter testing. Electronic meters have the potential of providing faster test times, multiple metering functions and calibration of the meter through software adjustment. However, implementing such functions can be expensive and complicated.
Presently, electric utility companies can test mechanical meters with a piece of test equipment which can reflect light off a metered disk to detect a painted spot as the disk rotates. An alternative form of testing mechanical meters is disclosed in U.S. Pat. No. 4,600,881xe2x80x94LaRocca et al. which describes the formation of a hole in the disk. A light sensitive device is placed in a fixed position on one side of the disk. As the disk rotates, and the hole passes over the light sensitive device, a pulse is provided indicating disk movement.
Since electronic meters preferably do not contain rotating disks, such simple testing techniques cannot be utilized. Consequently, a need exists for an electronic meter having a relatively simple means of testing the meter.
The previously described problem is resolved and other advantages are achieved in an apparatus for metering electrical power and electronically communicating electrical power information in accordance with sensed analog voltage and current signals. The apparatus comprises a first processor which receives the analog voltage and current signals and converts the analog voltage and current signals to digital voltage and current signals, a second processor which receives a metering signal and outputs at least one output signal based on the metering signal, and an output device which receives the at least one output signal and communicates the electrical power information external to the apparatus in a format specific to the output device.
The first processor determines at least one type of metered power based on the digital voltage and current signals and outputs the metering signal representative of the at least one type of metered power to the second processor. Additionally, the at least one type of metered power may comprise real power, reactive power, and apparent power. Still further, the first processor may receive plural phases of analog voltage and current signals, at least two of the plural phases being input to respective analog to digital converters to be converted into the digital voltage and current signals.
In accordance with a feature of the present invention, the output device comprises a display having a plurality of visible annunciators, and the at least one output signal comprises a display signal generated by the second processor to selectively activate the visible annunciators. The metering signal may be representative of a direction and rate of power flow and the display signal may be representative of the direction, such that the display signal selectively activates the visible annunciators to indicate the rate and direction of power flow. Further, the visible annunciators may be selectively activated such that rotation of a disk is mimicked and positioned on the display such that the rate of the power flow, the rate of disk rotation and the direction of power flow can be concurrently displayed. At least one of the plurality of visible annunciators may be activated at the rate of power flow based on a unit of power of the at least one type of metered power, such as the Kh value of the apparatus. The display may additionally alternately display a plurality of metered powered types in accordance with the display signal output by the second processor. It may also be preferable to display all visible annunciators in response to the display signal, and the display may comprise a liquid crystal display.
In accordance with another feature of the present invention, the output device comprises an optical port and the at least one output signal comprises an asynchronous communication signal, such that the optical port transmits information by converting the asynchronous communication signal to a predetermined wavelength of light. The optical port is adapted to receive and convert the predetermined wavelength of light to the asynchronous communication signal, and the second processor is capable of receiving commands input to the optical port via the serial asynchronous communication signal. In addition, the second processor selects the at least one type of metered power from a plurality of types of metered power such that different metered power types can be transmitted from the optical port at different times based on a control signal received by the optical port. The metering signal may be further representative of a direction and rate of power flow and the asynchronous communication signal and the information transmitted by the optical port is further representative of the rate of power flow. Additionally, the second processor may select a plurality of types of metered power and multiplex the plurality of metered power types over the optical port such that the plurality of types of metered power are transmitted by the optical power. Still further, the second processor may acknowledge an input from the optical port by echoing the input, wherein the input places second processor into a condition to receive additional data from the optical port, and the second processor may be programmable using the optical port.
According to yet another feature of the present invention, the output device comprises an option connector and the at least one output signal comprises a serial communications signal. The option connector is adapted to receive the serial communication signal, and the second processor is capable receiving commands input to the option connector.
In accordance with another aspect of the present invention, there is provided an apparatus for metering electrical power and electronically communicating electrical power information, where the electrical power comprises voltage and current characteristics determined in accordance with sensed analog voltage and current signals. The apparatus comprises a first processor which receives the analog voltage and current signals and converts the analog voltage and current signals to digital voltage and current signals, a second processor which receives a metering signal and outputs at least one output signal based on the metering signal, a non-volatile memory which stores configuration information, and an output device which receives the at least one output signal and communicates the electrical power information external to the apparatus in a format specific to the output device. The first processor determines at least one type of metered power based on the digital voltage and current signals and outputs the metering signal representative of the at least one type of metered power. The first processor and the second processor determine the at least one type of metered power in accordance with the configuration information stored in the non-volatile memory.
According to a feature of the invention, the output device comprises a display having visible annunciators, wherein one of the visible annunciators is made visible at the rate determined in accordance with a unit of power of the at least one type of metered power, and the rate is a predetermined fraction of the unit of power and is set in accordance with the configuration information.